Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2002-03-18
2004-03-16
Lester, Evelyn (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C345S105000
Reexamination Certificate
active
06707590
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a process of controlling the color-change process of several electrochromic glazings, where the color change of each individual electrochromic glazing is controlled within the color-change interval between an initial value T
start
and a final value T
end
by an individual control unit and where the individual control units are activated by a central monitor unit.
Electrochromic glazings are increasingly being used where variable solar control or variable light transmission is desired. Various constructions are used for electrochromic glazings. Usually, electrochromic glazings comprise electrochromic elements with a tungsten-oxide-base electrochromic layer. Such electrochromic elements in particular have proved suitable for large-area glazings where, in addition to the electrode layers necessary for application of electric voltage, as counterpart to the tungsten oxide layer, a transparent oxidic counter-electrode layer acting as ion storage layer and a polymer electrolyte layer arranged between the two are present.
The light transmission of electrochromic glazings is usually varied by the application of a voltage to the electrode layers or by impressing a current. Here, on the one hand the endeavor is to cause the color-change process to take place as rapidly as possible, where it is fundamentally desirable to operate with voltages or currents which are as high as possible. On the other hand, it is necessary to ensure that the electrochromic element of the electrochromic glazing is not permanently damaged by excessive voltages or by the flow of excessively high currents. It is necessary to take into account that the permissible voltages or currents are dependent inter alia on the area and the temperature of the electrochromic glazing. This temperature dependence is especially pronounced in the case of electrochromic elements with polymer electrolyte layers.
2. Discussion of Related Art
From WO 98/37453, a self-calibrating control process for electrochromic elements is known where an electrochromic element is assigned a control unit which regulates the voltage applied to the electrochromic element for a color change as a function of the temperature, of the current flowing and of a series of specified parameters independent of format. The previously known control process serves primarily to set the extreme states “fully colored” or “fully bleached”. It also permits however the setting of intermediate states. The electrochromic element activated in this way can, with the aid of a control unit assigned to it, be set individually to any desired transmission state between the extreme states.
It is known practice to activate several electrochromic glazings with the aid of a central monitor unit and in this way to initiate a color change process simultaneously in several such glazings. It has been found that, on account of differing temperature and differing sizes of the individual glazings, significant differences can occur in the color change velocity of the individual glazings, which leads to the light transmission values of the individual glazings occasionally differing significantly from one another during the color-change process. This leads to an inhomogeneous appearance of the glazings, which is generally undesirable.
The invention is based on the technical problem of improving known control processes such that it permits a largely uniform color change of all simultaneously color-changed electrochromic glazings, without of course excessively prolonging the duration of the color-changing process.
The solution to this problem is the subject of claim
1
. Advantageous developments will be found in the Subclaims.
SUMMARY OF THE INVENTION
According to the invention, the color-change interval is subdivided into a plurality of subintervals. The color change of the electrochromic glazings takes place step-by-step over these sub-intervals controlled by the individual control units; the central monitor unit does not initiate color change of the electrochromic glazings over a new subinterval until all satisfactorily operating glazings have completed their color change over the preceding subinterval.
Of course, the sizes of the subintervals should be so small that any light transmission differences between individual electrochromic glazings are not visible to the normal observer during color change over a subinterval. It has been found that this can be reliably guaranteed for example with tungsten-oxide-based electrochromic glazings if the size of the subintervals is chosen such that the light transmission factors of the individual glazings during color change over this subinterval differ from one another by a maximum of 5%, preferably at most 3%. The subintervals should not be too small, as on the one hand with decreasing size of the subintervals, measuring errors will increasingly impair the control accuracy of the individual electrochromic glazings, and on the other hand the complexity of control and monitoring as a whole will increase. It has been found that a value of approximately 2% for the variation of the light transmission factor of the electrochromic glazings within a subinterval represents the lower limit which, for the reasons stated, should not normally be undershot.
Observance of the aforementioned maximum deviation of the light transmission factor of individual glazings from that of the other glazings during a subinterval of a color change process can be guaranteed, irrespective of the dimensions and of other variables determining the rate of color change, by the size of the subintervals being chosen such that the light transmission factor of the electrochromic glazings during color change does not vary over each subinterval by more than this maximum permissible light transmission factor difference (which, as already stated, is from experience approximately 5%). It is also possible however, with a known installation situation and with known staggering of size of the glazings whose color is to be changed simultaneously, for the subintervals to be greater, as long as it is ensured that in any case under normal circumstances the light transmission factor of the individual glazings does not deviate at any time by more than 5% from that of the other glazings. In this connection, it has of course to be taken into account that even the glazing changing color slowest, at the time when the glazing changing color fastest has already completed a subinterval, has also covered at least part of the subinterval, so that the actual light transmission factor difference between all glazings involved in combined color change is, at all times during the color change over a subinterval, less than the difference of the light transmission factor of the electrochromic glazings at the beginning and at the end of the subinterval concerned.
The invention is also of course applicable with suitable adaptation to arrangements where the central monitor unit imparts to the control units light transmission values which are not nominal ones, but are different manipulated variables characterizing the state of tinting, for example “100” for “fully colored” or “0” for “fully bleached”. In these cases as well, the subintervals are to be set according to the invention such that the differences in light transmission factor of the individual glazings remain imperceptible at any time, and in particular do not exceed approximately 5%.
The percentages for the subintervals are of course to be regarded as percentage points, not as relative values. Thus, according to the invention, with a color change from a light transmission factor of 50% to a light transmission factor of 20% and with a specified subinterval value of 5%, a color change will initially take place step-by-step to a light transmission factor of 45%, then to 40%, and so on down to 25% and finally to 20%. In this context the stated values for the light transmission factor are nominal desired values for control of the electrochromic glazings, not necessarily genuine measured light
Flabeg GmbH
Lester Evelyn
Marshall & Melhorn LLC
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